Abstract

Game theory has been used to investigate a wide range of evolutionary questions, and has been important in explaining apparently selfish patterns in animal behaviour, and behaviours that do not appear to benefit the individual. The modelling chapters in this thesis develop new game theory approaches to modelling animal conflict, investigating the acquisition of territories and the trade-offs that occur between behaviours.

Many game theory models of conflicts between individuals make predictions regarding the duration of fights in relation to asymmetries in resource holding potential (RHP). Duration is often interpreted as a result of mutual assessment of RHP, allowing the weaker individual to avoid costly interactions. However, the duration of a contest may also be the result of each individual persisting to a threshold determined by its own RHP, in fiddler crabs, Uca mjoebergi, I show that duration of contests increases with increasing size of the loser, and decreases, but to a lesser extent, with increasing size of the winter, suggesting that neither the mutual assessment or individual threshold hypothesis can explain fight duration in this species. Instead, individual cost thresholds may determine duration, but larger opponents may inflict costs more rapidly, consistent with the cumulative assessment game of animal conflict.

In animal contests, the larger opponent is often victorious, but contests are often initiated by individuals that have little chance of winning (generally smaller individuals). A number of hypotheses may explain this behaviour, including a lack of alternative options (the ‘desperado effect’). Recent work has suggested that likely losers attack first due to an error in perception: they mistakenly perceive their chances of winning as being greater than they are. Using a game theoretical model, I show that if smaller individuals can accurately assess their chance of winning, if this chance is relatively high, and if they have few alternative options, they are predicted to be as aggressive as their larger opponents. In addition, when resources are abundant, and small individuals have some change of winning, they may be more aggressive than their larger opponents.

Using a game theory model, I show that avoidance of a single fight location can be adaptive if the benefits of access to the area are low compared to the costs of fighting. Low fight costs and high population densities lead to the break down of territoriality and the formation of large, overlapping home ranges.